The present invention relates to closures for environmental protection of butt splices in cables (i.e. a splice in which the cables are aligned end to end facing in the same direction), and to cable splices incorporating such closures.
U.S. Pat. No. 4,924,034 discloses an enclosure for providing environmental sealing around a cable butt splice. The enclosure disclosed has a first tubular part through which the cables extend and an outlet in that tubular part through which they enter and leave the enclosure. The enclosure also has a second part which is hollow and closed at the end remote from the first part. When first installed around a butt splice the enclosure is a single unit in which the first and second parts are Joined together, but if it becomes necessary to obtain access to the cable splice after the enclosure has been installed, this is done by cutting the enclosure along a line between the first and second parts, and removing the second part. The relative sizes of the first and second parts are arranged such that, after cutting the enclosure, it can be reconstituted by sliding the second part into or over the first part. The two parts have flanges which may be clamped together when the first and second parts have been slid together, and a sealing washer may be provided to give an improved seal between the flanges. Sealing of the cables passing through the outlet of the enclosure is obtained by providing a heat-recoverable portion of the outlet.
The present invention provides similar telescoping parts of a cable enclosure. In the present invention, however, sealing both (i) between the telescoping parts of the enclosure, and (ii) between the cables and the enclosure, is achieved using an inflatable sealing member within the enclosure.
Inflatable sealing members are known. It has been proposed, for example, to seal ducts carrying cables, e.g. telecommunications cables by using inflatable sealing members within the ducts. The inflatable sealing members may carry sealing material (e.g. mastics, gels) which come into contact with the duct or cables within the duct when the sealing member is inflated. Such a sealing system is disclosed for example in WO092/19034 and WO094/05943, the entire disclosures of which are incorporated herein by reference.
WO 92/19034 describes an inflatable envelope, the envelope being inflated in use by introducing a pressurising medium into the envelope through a hole in the walls of the envelope by means of a probe passing through the hole, and a gel material being provided to seal that hole on withdrawal of the probe. This inflatable envelope may be used to form a seal between a single cable passing through a duct by wrapping the envelope around the cable, inserting the envelope-wrapped cable into the duct, and then inflating the envelope. Similarly for two cables in the duct, or in a splice, two of the said envelopes can be wrapped around the cables, and between the cables before inflation.
Where there are multiple cables passing through a duct it is also known from British Patent Application 9403838 to use one or more devices capable of co-operating with an outer pressure member (e.g. an inflatable envelope or sealing member of the type described in WO92/19034) to form a sealing block between the cables and the duct. The devices used and described typically comprise (i) an elongate support member and (ii) two flexible mastic leaves secured relative to and extending laterally of the elongate support member. In use, the devices are positioned between the cables and co-operate with the action of the outer pressure member to form a sealing block between the cables and the duct. Where there are up to four cables entering the duct a single device may be used in combination with the outer pressure member, but where there are five or more cables, two or more of such devices may be used.
As mentioned above the enclosure of U.S. Pat. No. 4,924,034 relies on the application of heat to ensure sealing of the cables to the enclosure (using heat recoverable material at the outlet to the closure). In some situations the use of heat is undesirable, as the cables may be sensitive to heat. Also the enclosure of U.S. Pat No. 4,924,034 is not reusable as such. The first time a re-entry has to be made it is necessary to cut the closure into two sections. This has to be done at the location at which the enclosure is installed. If additional cables have to be inserted then heat shrink material sealing the original cables will have to be cut away. Re-sealing the enclosure after re-entry will then involve two separate sealing operations, with two separate sealing components (one at the junction between the two closure parts, and the other around the cables at the outlet).